Ball grid arrays (BGAS) are utilized for connecting electronic components, such as integrated circuit chips, to circuit boards. Typically, the electronic components in the circuit boards each include a plurality of contacts. Typically, contacts on the circuit board will be arranged in patterns on different areas of the circuit board to match the pattern of contacts on electronic devices, such as chips and chip carriers, that are to be attached on specific locations on the circuit board.
BGAs typically include at least one ball of solder arranged between the electronic component and the circuit board at each contact so as to electrically connect the electronic component to the circuit board. BGAs replace perimeter pins with solder balls to directly attach the electronic component to the circuit board. Thus, BGAs permit a reduction in the number of leads in a given package size, increase I/O density for a given package size, among other advantages.
Additionally, the BGAs can be self-aligning during reflow. This is at least partially a result of surface tension of the solder. The surface tension of the solder pulls the solder into the smallest possible shape.
Additional information regarding BGAs and BGA packages is provided by "IBM Details Its Ball-Grid Array Push," Electronic Engineering Times, Aug. 9, 1993, and "Ball Grid Arrays: The Hot New Package," Electronic Engineering Times, Mar. 15, 1993. The entire contents of these two articles is hereby incorporated by reference.
To attach the electronic components to circuit boards, the solder balls are first attached to the side of the electronic component to be attached to the circuit board. Typically, attaching solder balls to an electronic component is accomplished by placing the solder balls in contact with the electronic component and raising the temperature of the solder balls above the melting point. The solder balls are then cooled.
The electronic component and BGA typically are attached to the circuit board by placing the electronic component and BGA in contact with desired location on the circuit board. The temperature of the solder is then caused to rise above the reflow temperature of the solder. As the solder cools, it secures the component to the circuit board or other substrate.
Typically, heating the solder to attach the component to the circuit board is carried out by exposing the electronic component and, hence, the attached solder balls to heated gas. This operation typically is performed in a convection reflow furnace. The electronic component and attached solder balls are heated through convection of heat from the gas to the electronic component to the solder balls. These solder balls may also be heated directly by contact with the hot gas.
During the process of attaching electronic components to circuits boards, all of the connections might not be successfully made between the electronic component and t he circuit board by the solder balls. Such instances may be detected by testing the component prior to advancing the circuit board to further processes or incorporation into other devices. Additionally, during the operation of a device including the circuit board, some of the connections may fail.
Whether failures of connections occur prior to or during operation of a circuit board that includes the BGA, the electronic component may need to be reheated to remove it from the circuit board. Hot air devices such as shown in FIG. 1 are also typically used for this "rework" process as well. FIG. 1 illustrates one example of a known device utilized for heating electronic components and attached solder balls to attach the component to a circuit board. An additional reason for removing an electronic component from a circuit board is to replace it with a new component in the event of improvements to the component. Such removed components may be repaired or replaced.
A micro ball grid array (.mu.BGA) is a subset of the generic ball grid array. Typically, a .mu.BGA is characterized by having a ball-to-ball spacing of about 30 mils or 0.03 inch or less. Typical BGA packages have a pitch of about 50 mils. Commonly, .mu.BGA is in a chip scale packaging family which is defined as package size being no larger than 1.2 time the die size. Because of their small footprint, .mu.BGA devices are designed to be placed in close proximity on a circuit board.